1. Technical Field
The present invention relates to a display system, and an image output device and an image display device that are used in the display system.
2. Related Art
Traditionally, an image display device such as a projector which forms and displays an image corresponding to inputted image information is known. In many cases, such an image display device is connected to an image output device such as a PC (personal computer) and thus used as a display system.
Images outputted from the image output device and displayed by the image display device are roughly divided into natural images and non-natural images. Of these, natural images are images of landscapes and so on and are often dynamic images, for example, as shown in movies. Meanwhile, non-natural images are images of letters, graphic patterns and so on and are often still images, for example as shown in graphs and tables used for presentations. Even if such natural images are compressed to a certain degree, deterioration of the images due to compression is not conspicuous. However, deterioration of non-natural images tends to be conspicuous since these images have many areas containing straight lines.
Thus, a digital camera is known which switches compression systems for an image to be saved between pickup of a natural image and pickup of a non-natural image (see, for example, JP-A-2001-218065). Also, a calligraphic and painting works photographing device is known which compares a picked-up image with a immediately previous picked-up image that is acquired, and then picks up the image with high resolution if there is no change between the images and the picked-up image is different from a reference image, or picks up the image with low resolution if there is a change between the images and the picked-up image is the same as the reference image (see, for example, JP-A-2007-259372).
However, the digital camera described in JP-A-2001-218065 has a problem that the user needs to switch modes between pickup of a natural image and pickup of a non-natural image.
The calligraphic and painting works photographing device described in JP-A-2007-259372 compares a picked-up image with a immediately previous picked-up image. Therefore, the device has a problem that a storage unit to save the immediately previous picked-up image that is immediately before (an image of at least one frame) is needed for the comparison between the images and this makes the device expensive.